Portable and emergency equipment for inductive carrier communication systems



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PORTABLE AND EMERGENCY EQUIPMENT FOR INDUCTIVE CARRIER COMMUNICATION SYSTEMS I Filed May 25, 1950 4 Sheets-Sheet 4 A. (7 Solute.

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Q: M m (l 57081 26905 v v" N BY 1 Patented Nov. 6, 1951 PORTABLE AND- EMERGENCY EQUIPMENT FOR INDUCTIVE CARRIER COMMUNICA- TION SYSTEMS Edgar W. Breisch, Edgewood, Pa., assignor to Westinghouse Air Brake Company, a corporation of Pennsylvania Application May 23, 1950, Serial No. 163,590

9 Claims. 1 My invention relates to portable and emergency equipments for inductive carrier communication systems, and moreparticularly to portable and emergency equipments for inductive carrier communication systems for railway trains.

In communication systems for railway trains, communication is usually provided between the front and rear ends of a train, between different trains, and between a train and away side station. Also, portable equipments have been provided for such train communication systems. Such a portable equipment is carried by a trainman when inspecting the train and doing fiagging and switching duties and by it the trainman is enabled to keep in better touch with the other members of the train crew and also with the operator of any nearby tower. Such a portable equipment is also useful at the location of an accident or at the location where some special work is being done and therebyenable the wreck master and work supervisor to keep in touch with the crew of trains in the vicinity of the particular location.

In view of the foregoing conditions for railway train communication systems, a feature of my invention is the provision of novel and improved portable equipment for. inductive carrier communication systems.

Another feature of my invention is the provision of portable equipment that can be used as an emergency wayside station for railway train communication systems.

Again, a feature of my invention is the provision of improved portable railway train inductive carrier communication equipment that can be operated either from a self-contained battery or from a power supply line.

Other features, objects and advantages embodying my invention will appear as the specification progresses.

The apparatus set-forth in the present application is similar in certain featuresto that disclosed in a prior copending application for Letters Patent of the United States, Serial No. 139,093, filed January 17, 1950, for Transmitting and Receiving Circuits for Inductive Carrier Communication Systems, by Kenneth E. Doriot, and the said copending application contains claims covering certain improvements in the inductor structure 'which is disclosed but not claimed in the present application.

The foregoing features, objects and advantages of my invention are obtained by the provision of two portable units which are preferably of like size and appearance. The apparatus of the first unit includes a light weight portable housing, 'a T transmitter and a receiver which are capable of using a given carrier communication or telephone current, a combination transmitting and receiving loop circuit, a power pack make up of dry cell batteries, and a handset. The housing is a sturdy fiat rectangular case of the conventional suitcase form and which case is provided with a handle and a shoulder strap to enable the unit to be carried by a trainman'at his side as he goes about his duties. The case is of light weight material and of a structure to prevent the entrance of moisture under adverse weather conditions, and due to this constructure the unit is capable of being used at outdoor locations. A hinged door is provided as a major section of one side wall of the case to allow ready and convenient access to the apparatus. The case is constructed with means whereby a weathertight seal is formed when the door is closed.

The transmitter and receiver are assembled on a single chassis secured inside the case a given distance above the bottom of the case. The power pack includes a small box in which the dry cell batteries are placed and which box is designed to fit inside the case adjacent one end of the chassis.

The transmitting and receiving loop circuit is mounted in a shallow recess formed in the inside walls around the inside periphery of the case. This loop circuit constitutes an air core coil having an area substantially equal to that of the case. The size of the electrical conductor and number of turns of the coil are selected to provide a' desired inductive relation with the transmitting line circuit, the coil being further selected as to its size so that it will go in a case which is nottoo large to be easily carried. This coil is connected to the output of the transmitter and to the input of the receiver in such a manner as to form a combined transmitting and receiving loop circuit.

The handset is provided with a push-to-talk switch and a retractile cord and it is supported in a cradle or hook switch in an enclosing recess built in the door, the handset being available from the outside of the case. Terminals and a plug connector receptacle, together with a voltmeter, are mounted in the top of the case. It is to be seen from the foregoing description of the case that all vital parts of the apparatus of the first unit are confined within the walls of the case and there are no projecting elements which may be easily demaged or which may endanger the one carrying the unit by catching onto cars or other equipment.

The actual use of the first unit requires only 3 the removal of the handset from the hook switch and the closing of a battery switch, the apparatus being normally set to receive when the battery switch is closed. To send, the push-to-talk switch is closed to switch the power pack from the receiver to the transmitter. Thus, the first unit alone constitutes a portable equipment having a self-contained power source and which equipment provides two-way one channel com munication with other equipments of the system. such other equipments being an equipment mounted on a locomotive, in a cabin car, or at a wayside tower, or another portable equipment. The apparatus of the second unit comprises a light weight portable housing, an alternating current power line connection and a transformerrectifier network for converting alternating .current into direct current, an audio amplifier with a loud-speaker, a call oscillator, and a control relay. The housing is a case which is preferably of the same size and construction as the case of the first unit. The two cases are constructed substantially alike to economize the manufacturing thereof, to provide a pleasing appearance when they are used together and to facilitate the practical use of the two units. The second unit also includes a plug connector receptacle which is constructed to cooperate with the plug connector receptacle of the first unit to enable the apparatuses of the two units to be interconnected by a cable the two ends of which are provided with plug units. This interconnecting cable and a power line circuit connecting cable are carried inside of the case of the second unit when not in use.

When the two units are to be used together, the interconnecting cable is plugged into the two connector receptacles and the power line connecting cable is connected to a commercial alternating current power circuit. When the alternating current power is applied to the second unit, the dry cell battery of the first unit is automatically disconnected and the power for the aparatus of both units is supplied from the transformer-rectifier network. Thus when the two units are used together they constitute an emergency wayside station which can be powered from a commercial power line and which station provides two-way single channel communication with either train carried stations or other wayside stations.

It should be here noted that in inductive carrier train communication systems the existing line wires and other conductors paralleling the track are used as the transmitting medium or circuit for conveying the communication current along the railway. These line wires and other conductors are elements of the transmitting medium due to the longitudinal circuit formed by the line wires and other conductors, the distributed im pedance of the line wires and other conductors to ground, and the ground return path. The equipments of two remote stations are brought into communication relationship with each other by each equipment being provided with circuit elements which are arranged for electrical coupling with the transmitting medium.

I shall describe one form of portable and emer- .4 Figs. 3 and 4 are side and end views, respectively, showing the first unit, Fig. 3 showing the inside of the case when the door is broken away, and Fig. 4 being a sectional view taken on the line .IV-IV of Fig. 3. Figs. 5 and S are side and end views, respectively, showing the second unit, Fig. 5 showing the inside of the case with the door broken away and Fig. 6 being a sectional view taken on the line VI--VI of Fig. 5. Fig. 7 is a diagrammatic view showing interconnecting circuits that may be used with the apparatuses of the first and second units embodying the invention.

.In each of the several views like reference characters designate similar parts.

Referring to the drawings, the reference characters [U and 2U designate a first and a second unit of the equipment. Looking at the first unit I U, its construction comprises a case IU of any suitable material, such as fiber or plywood covered with fiber. This case I0 is preferably of a fiat rectangular shape, that is, it is made in the shape of a conventional suitcase, the dimensions of which are determined as required to house the apparatus of the first unit. The two longitudinal walls of the case form a top and a bottom panel, respectively, and the case is provided with a handle grip ll of suitable material,

gency equipment embodying my invention and such as leather, secured to the top panel of the case. Also, an adjustable shoulder strap 9 of webbing material is provided with snaps l2 which snap into rings I3 which are secured one in each end wall or panel of the case. It follows that the case [0 can be carried by a trainman either by the handle II or by the shoulder strap 9, the case hanging at the side of the one carrying the unit.

A hinged door I4 is provided as a major portion of the front wall or panel of the case Ill. The size of the door allows ready and convenient access to the interior of the case. Two slotted head machine screws I5 are anchored in the top edge of the door. The screws 15 engage with threaded members l5 anchored to the top panel of the case so that pressure is applied against a resilient gasket I! to form a substantially weathertight seal when the door is closed and the machine screws I5 are run down. The lower portion of the case lflis of a solid box-like construction to give the case strength and to enable it to be set upright on the ground. In order to prevent the entrance of moisture under adverse weather conditions, all seams of the case are covered with strips I8 of heavy gauge material, such as fiber, and which strips are riveted to the case at a reasonably close spacing. The bottom corners are protected with formed metal members I9 which have extended embossed pads 20 to serve as feet. The top corners are similarly protected except the sections are without feet. The entire outside of the case is coated with suitable weatherproofin paint.

As best shown in Fig. 3, a chassis 2| of suitable light material, such as aluminum, is secured inside the case by rivets or screws. The chassis 2| is positioned some distance above the bottom of the case audit is made to extend a given portion of the length of the case. The chassis is formed for the mountin of the various elements of the transmitter and the receiver and the control relays of the unit. These elements are outlined by light'lines in Fig. 3, the specific structure of the elements forming no part of the present invention.'

Adjacent to the chassis 2i and atthe righthand end of the case as viewed in Fig. 3,'there is housed a battery box compartment 22 of any suitable material. This battery box is of a size preselected for the box to house dry cell batteries which when connected together electrically supply the necessary voltages for the diiferent electron tube circuits of the transmitter and receiver.

As best shown in Figs. 3 and 4, a recess 23 is formed around the inside walls of the case H] to extend the full longitudinal inside periphery of the case. In this recess 23 there is mounted a combined transmitting and receiving 100p circuit coil 24. This coil 24 is made up of a selected number of turns of insulated wire of suitable gauge and it is connected to the transmitter and receiver in a manner to be described hereinafter. This coil 24 forms an air core inductor which has an area which is substantially the same as that of the case l0. With this loop circuit coil mounted inside of the case, it is protected against coming in contact with the person carrying the unit. Also, the coil is protected against mechanical injury due to the unit being carried about. Thus the gauge of the wire used to make up the coil 24 need not be any larger than required to provide the desired electrical characteristics. For reasons to appear hereinafter, the loop circuit is preferably provided. with a second coil 43 (see Fig. '7), the two coils 24 and 43 being independent coils. As will be apparent by an inspection of Figs. 3 and 4, the size of the case I is determined largely by the desirable size of the air core coil for the unit.

The door I4 is formed with a recess 25, the dimensions of the recess 25 bein selected suitable for a standard size handset HS to be carried in a cradle or hook switch 26 within the recess. This handset HS is provided with a retractile cord 21 having conductors by which the handset is connected to the transmitter and receiver in a manner to be described when the operation of the unit is described. The cord 21 enables the unit to be used while carried by a trainman and also used by an operator several feet away when the unit is set down on the ground. In the recess 25 and just below the hook switch 26 there is mounted a toggle switch 28 for governin the connections of the batteries of the unit in a manner to later appear.

The top panel of the case has mounted thereon line and ground connection terminals 29, a plug connector receptacle 30, a battery output indicator switch 3|, and a dual range weather sealed voltmeter 32, and each of which elements is connected to an associated element of a transmitter and receiver of the assembly by suitable cable connections.

The unit 2U is provided with a case 33 which is preferably of substantially the same size and construction as the case I0 of the first unit, except the case 33 is provided with a carrying handle 34 but with no shoulder strap. It is clear, however, that the case 33 can be provided with a shoulder strap similar to the strap 9 if desired. Also, as shown in Figs. 1 and 5, a door 35 of the case 33 forms a major portion of the back wall or panel of the case, whereas in case ll) of unit IU the door I4 is formed in the front panel of the case. Furthermore, the door 35 of the second unit is without a handset recess. In the front panel of the case 33 of the second unit a loudspeaker LS is mounted.

A chassis 36 is secured in thecase 33 as by rivets and screws, the chassis 36 extending the full length of the case. Mounted on this chassis 336 are the necessary components of an amplifier, a call or callin tone oscillator, a power pack including a transformer-rectifier network and an alternating current power connection, and a control relay, these various elements of the apparatus.

of the second unit being indicated by light lines in Figs. 5 and 6. In the top panel of the case 33 there are mounted a receptacle 31 for an alternating current power line cable, a power switch 45, a line voltage switch 38 (see Fig. 1), a call signal control switch 39, and a plug connector receptacle 40. It follows that this second unit can be carried to a designated point independent of the first unit and connected to any suitable source of alternating power by means of the line cable receptacle 31. Also, the second unit can be interconnected to the first unit by a suitable cable CC being plugged into the receptacles 40 and 30 of the two units. When thus connected the two units can be used as a two-way single channel wayside station.

The apparatus and circuits of the two units IU and 2U are shown diagrammatically in Fig. '7. The apparatus and circuits of the first unit 1U are shown to the left of the dash and dot line 4| and those of the second unit 2U are shown to the right of the line 4|. Looking at the apparatus of unit IU, the primary devices comprise a transmitter TA, a receiver RA, a power pack PP, a handset HS, a loop circuit LC, and control relays RI and R2.

The transmitter TA comprises a modulatoroscillator MO and a power amplifier PA shown in block form. These assemblies may take any one of several forms for supplying a modulated communication current. It is sufficient for the present application to point out that the modulator-oscillator MO may include a carrier oscillator having an input connected across a resistor 42 in such a manner that the carrier is frequently modulated by voice frequencies applied across the resistor 42. Also, the output of the oscillator is connected to the input of the power amplifier PA. The power amplifier PA may take any one of several forms of amplifiers and the output here includes the coil 24 of the loop circuit LC. The receiver RA includes a carrier amplifier CA and a demodulator DU which are shown in block form since they can be of any one of several known arrangements for such devices and when used with the apparatus of the transmitter referred to above they would use a frequency modulated carrier current similar to that supplied by the transmitter. The amplifier CA may be of any standard form suitable to amplify a frequency modulated carrier telephone current and the demodulator DU may be of the superheterodyne form suitable to mix the output of the amplifier CA with local oscillations and supply to the primary winding 44 of an output transformer Tl a voice frequency current.

As an aid in understanding the apparatus, I shall assume that a carrier of 144 kc. is used and this carrier is frequently modulated by a voice frequency band of 300 to 3000 cycles per second, but it is apparent that other frequencies can be used. Thus when the transmitter TA is energized and voice frequencies are applied across the resistor 42, a 144 kc. carrier current frequency modulated by the voice frequencies is supplied to the coil 24 of the loop circuit. Also, when the receiver RA is energized and electromotive forces of a 144 kc. carrier frequency modulated by voice frequencies are picked up by the coil 24 of the 71 100p; circuit, the; current isedemodulatedand voice frequency,- currentisisuppliedetov ,th rwinding z of ;thetransformer TI v 1 The power pack PP comprises a; high and-a low voltagefbattery, each of; which includes a selectednumber of dry; cells. The-high voltage battery is provided with several, terminals from which diiferent voltagesv can be obtained.; As shown, there are threeterminals indicated at I 35V, 250V, and 500V, from whichvoltages; of 135, 2,50. and 500 'volts canbe obtained. The low voltage battery provides but a singlevoltage of, say; 7.5-volts, the positive terminal of this battery being indicated'at 7.5V. The negativeterminals of the batteries are connected toground through the battery switch 28- and'the hook switchliin series.

The essential elements of the secondunit-ZU comprise a. power pack which includes a power transformer T2, afirst rectifier IR, a second rectifier; 2R and a voltage divider and filter network VD, and audio amplifier AA, a loud speaken-LS, a call or calling tone oscillator CO, andacontrol relay R3. The transformer T2 is provided with a primary winding 46 which is connected across the terminals of the power line receptacle 3? through the voltage switch 38 and the; power switch45, the arrangement being such that when the switch 45 is closed the full winding. is connected acrossthe terminals 31 through a first positionof-the switch 38, and a selected portion of the winding 46 is connected across the terminals 31 through a second position of the switch 38. The transformer T2 is provided with,four-independent secondary windings 41; 48, 49, and" 50; The winding 56 is connected to the input terminals of the first rectifier IR, the rectifier IR being preferably a full wave rectifier of. the dry surface contact type. The secondary windings 41 andABare connected to the second rectifier 2R, which is preferably a dual diode, the winding 41 having its outside terminals connected to the filament of the rectifier tube 2R, the outside terminals of winding 48 being connectedto the two anode elements of the tube 2R, the mid terminal of winding 48 beingconnected to ground and the mid terminal of the winding 47' being connected to the filter and voltage divider network VD. The arrangement of the power pack is such that a relatively low voltage 7.5 volts is applied to a terminal 1.5V of the second unit from the first rectifier IR, and several voltages are supplied at the different terminals ofthe voltage divider VD, the voltages of 500, 250 and 135 volts being supplied at the terminals 506V, 253V, and I35V, respectively. it is to be noted that these voltage terminals for the unit 2U correspond to similar voltage terminals of the battery of. the power pack PP of the unit IU.

The secondary winding 49 of the. transformer. T2 i connected to the heater elements of the tubes of the amplifier AA and the oscillator CO through a connection which is indicated by the circuit PI.

The audio amplifier AA is of standard form suitable to amplify voice frequency cur-rent an: pliedto its input. Preferably this amplifier in.- cludes tubes connected in a push-pull arrangement, and the output of the tubes includes, a primary winding 5| of a transformer, T3, a secondary winding 52- of which is connected to a resistor 53; having an adjustable terminal 54 and one outside. terminal connected to the operating windingof; the loudspeaker LS.

The call oscillator (20- isshown conventionally;

and; it iapreferably: of the-electron: tube :typearrangedato: supply; a predetermined-voice. frequency of 7 say; 1700 cycles persecond, such current, being usedasthe calling tone-.

Inusing theunit IU alone as a portable quipment,;the switch 285is closed to, prepare the connectionrof'the'powerpack PP to the circuits of the transmitter andreceiver. Then .when the hand: seteHSt-isremoved from it hook switch so that the switch; 25-,- is: closed; thelpower pack is connected to the-circuits. Normally-,- that is, when the-ape paratus: is in thestandby position, the receiver RA; is;energ-ized and the, transmitter TA is de-, energized; In energizing the receiver RA power is-appliedto-the heaters of the, tubes of the. re,- ceiver-pver acircuit which includes terminal 1.5V,- backcontact, 55' of; relay R2, back contact 56 of relay RI andwire- 5], the return side of the circuit. beingcompleted through ground. Power-is also supplied; from terminal I35V of. the power pack to the anode-circuits from the. tubes of -the receiver, this; circuit, including terminal I35V.. back contact 58;of relay R2, back contact 5950! relay RI. and'wire 60, the return side of the-cir-, cult being-completed through ground. Thus any electromotive force of the carrier telephonecurrent pickedup. by the coil 24- of the loop-circuit is applied to the inputgofthe receiver through the inputcircuit:v includingcapacitors l2 and I3 and the current, is amplified and demodulated and the voicefrequency current inducedin the winding 6|- of the-transformerrTl. This voice frequency current: thus induced'inathewinding 6| will inv turn be applied to the earphone. 62; of the headset through an obvious circuit-which includeswire 63 and the; ground connection.

Whenthe operator wishes to send, he will first press thepush button switch PB. The closing of switch PB completes a circuit for energizing.- the relay RI, the circuit extending from terminal 1.5;V. through back contact- 55 of relayRZ; winding of relay RI, wire 84, and switchPB to ground. The picking up of relay RI to open back contacts 56 and. 59,;removes power from the receiver RA. The closing of: front contact 56'of relay RI appliespower from. the terminal 1.5V to the heaters of the tubes of the devices MO and PA of the transmitter. Also, power. is supplied from terminal1250V tothe: anodes ofthe tubes of thedevice M0 through a circuit including back contact 64. of relay-R2, front; contact 65 of relay RI, and wire 66.; Furthermore, power isappliedfrom the high. voltage terminal 500V ofthe power pack to the. anode circuit of the power amplifier- PA:v through a circuit including back contact 61* of; relay R2, front contactBlqf-relay RI, Wire 69,,resistor 1D,: coil 24. of' the loop circuit, the anode circuit for the tubes of the Power. amplifier. PA and ground;,

Witlrtheclosing offront contact 56 of relay RI, the microphone circuit for the headset is formed, the-circuit extending from terminal-1.5V, through back contact 550i, relay R2, front contact 56 of; relay RI, resistor; 42, microphone II of the headset and" thence: through the ground, return to the battery. Thus the operator by speaking into the microphone M after, having pressed the push but-- ton PB will cause the voice frequencies of thespeech to be created acrossresistor 42 and ap-. plied to the transmitter and a correspondingfrequency modulated telephone current will be suppliedto the coil 24 of the loop circuit, the current flowing in the coil 24 being. available for. inducing; a corresponding,electromotiveaforcepin the transmittini. line circuit with, which the lo0p.circuit.h1

high voltage of the battery is blocked from the input of the receiver RA by means of the capacitors I2 and I3. It is to be pointed out that the inductor coil 24 can be disposed for its most efiec-' tive induction with the transmitting line circuit by moving the case to place the coil so that its vertical plane is parallel with the line wires.

When the two units IU and 2U are used together as an emergency equipment or as a wayside station equipment, the two units are inde-' pendently carried to the given location and placed side by side as illustrated in Figs. 1 and 2 and the connecting cable CC is plugged into the receptacles 30 and 40. Also, the connection of the alternating current power line is made to the receptacle 3! and the switches 38 and 45 are closed, the switch 38 being set at its first position or second position according as the voltage of the alternating current supply is high or low.

With the transformer T2 energized by-alternating current, a full wave rectified current of a voltage of 7.5 volts is applied to the terminal 1.5V of unit 2U through a filter network 89. Current then flows from terminal 1.5V of the second unit through wire 93, conductor B of the cable CC, wire 94, winding of relay R2 and ground, and the relay R2 is picked up. The picking up of the relay R2 serves to automatically disconnect the connection of the power pack PP of the first unit, the connection being opened at the back contacts of the relay R2. Also, a full wave rectified currentis supplied to the voltage divider VD from the transformer windings 41 and 48 through the second rectifier 2R so that the several voltages ap pear at the terminals of the voltage divider VD. Power is also supplied from winding 49 of the transformer T2 to the heaters of the tubes of the devices CO and AA of the second unit and these devices are in an active condition.

The receiver RA of the first unit is now powered from the power pack of the second unit, current flowing from the terminal 1.5V of the second unit to the heaters of the tubes of the receivers RA through a connection including wire 93, cable conductor B, wire 94, front contact 55 of relay R2, back contact 56 of relay RI and wire 51. The anode circuits for the tubes of the'receiver are powered from the terminal 135V of the voltage 1 divider of the second unit through a circuit that includes wire I4, cable conductor E, wire I5, front contact 58 of relay R2, back contact 59 of relay RI and wire 60. Furthermore, power for the anode circuits for the tubes of the audio amplifier AA is supplied from terminal 250V of the voltage divider of the second unit through back contact I6 of the relay R3 and the primary winding 5| of the transformer T3. Again, the input side of the audio amplifier AA is now connected across the winding 6| of the transformer TI of the receiver RA through a connection that includes wire- Il, back contact I8 of relay R3, wire I9, cable conductor G, wire 86, and the ground return. It follows that frequency modulated carrier telephone current picked up by the coil- 24 of the loop circuit is amplified and demodulated at'tbe re- 1'0 ceiver RA of the first unit and the voice frequency current is further amplified at the audio amplifier AA of the second unit and the voice frequencies reproduced at the loud speaker LS. It is also apparent that the speech is also reproduced at the earphone 62 of the headset because the earphone of the headset is still connected across the winding 6I of the transformer Ti. In order to send with the two units, the operator would press the push button PB, the closing of the push button PB being efiective to pick up relays RI and R3 in multiple. A first circuit path can be traced from terminal 1.5V of the second unit, through the winding of relay R3, wire 8I, one blade of switch 45, which switch is now closed, wire 82, cable conductor F, wires 83 and 84, push button PB, andground return. The other path of this circuit includes terminal l. 5V,"wire 93, cable conductor B, wire 94, front contact 55 of relay R2, winding of relay RI, wire push button PB and ground return. With relay RI picked up closing front contact 56, the connection from terminal 7.5V of the second unit is switched from the heaters of the tubes of the receiver to the heaters of the tubes of the transmitter TA, this circuit being the same as traced for energizing the relay i RI up to the winding of the relay and thence through front contact 56 of the relay to the tubes of the transmitter. picked up, the connection for power to the audio amplifier AA is disconnected at back contact I6 of relay R3, and power from the terminal 250V of the voltage divider VD of the second unit is supplied to the anodes of the tubes of the modulator-oscillator M0, the circuit extending from terminal 256V of the voltage divider through front contact I6 of relay R3, resistor 95, wire 85, cable conductor D, wire 86, front contact 64 of relay R2, front contact 65 of .1

relay RI, wire 66 and through the ground return. Again, power from the high voltage terminal 500V of the voltage divider is supplied to the anode circuit for the power amplifier PA by' a ciruit completed from terminal 560V of the voltage divider through wire 8I, cable conductor C,

the operator by speaking into the microphone II would cause a frequency modulated carrier tele'-' phone current to be supplied to the coil 24 of the loop circuit and this current will be available for inductively transferring energy to the line circuit with which the coil is positioned for inductive relationship.

It follows from the above that with the two units connected together, two-way conversation can be carried on by the operator opening and closing the push button PB to'alternately energize the receiver and transmitter of the first unit from the power pack of, the second unit. During the reception of a message, the message will be reproduced at both the loud-speaker LS and at the headphone 62.

In systems of the type herecontemplated, a

calling tone is frequently provided so that an op- With the'two units IU and 2U used together in the manner explained hereinbefore, a calling current can be generated by the call oscillator CO" and a calling signal sentout through the transerator can call desired remote stations.

With the relay R3 ant-area l1; mitter TA. To send arcall, the switch 3941s closed,

while the push button PE -'isalso closed to pick up the relaysRl andiR3; Withirelay R3-picked tion including a'coupling capacitor 9|; front contact 18' of relay'R3; wire. 19, cable conductor G,.

wire '80, a coupling capacitor 92, resistor 42* and ground-through heater circuits. Thus, a calling current is'supplied to the-coil and is available for transferring energy to theuassociated transmitting circuit. It is'tobe noted that: by recurrently opening and closing, the switchv 39- the calling signal can be coded.

When the: two unitsare used -.as-an emergency wayside station itmaybe desirable to coupledl rectly to a pair of line wires; Thiscan berdone by connecting the line wires'one tothe top and one to the: midterminal 291 and-connecting the bottom terminal'H-to ground. The. energy-:in duced in coil l-a due to current flowing in coillk will be supplied to the line-wiresand' current received from the line- -wiresswill be transferreditocoil it through the coil;

Although I have herein-shown andv described but one form'of portableandemergency equipments I for inductivercarrier communication systems embodying'my invention, it is understood. that various changesand.modifications may be made therein wihin'the scope of the appended claims without departing from the spirit and scope of my invention;

Having thus describechmy invention, what I claim is:

1. In a portable equipmentiunit'for a-two-way inductive carrier communication system which uses a transmitting line circuit, the combination comprising, a flat rectangular 'c'aseaof' a: selected light weight material andprovided" withmeans: to'enablethe case to be carried, an-assembl-y'im' cluding a transmitter and a receiver of carrier communication current mountedzin said'case, the inside: walls of said case-formed with a recess which extends for" the fulllongitudinal inside periphery of the: case; a coil-of a given number of turns of an electricaLconductor secured insaidrecess, and said coil beingprovided withconnections to the output'of saidtr-ansmitter and tothe input of saidreceiver, said coil forming-an air core inductor which is fully confined: within saidcase tobe free from contact. and mechanical injury when the case is: being carried and which inductor'can be positioned for eilectivetransmissionrandreception by induction by proper posir tioning of thecaset 2. Ina portablev equipmentunit for atwo-way communication system, the combination com-- prisingra'suitcase form. of ahousingof a selected. light weight material and having means to. en able the housing to be carried, an assembly including a transmitter and a receiver of carrier. communicationacurrent mountedrin: said housing: an air core coilof a-selected electrical conductor mounted in said housing and provided with-connections to: the output-ofsaid-transmitter. andito the input of saidreceiver. in multiple. a airhandset a selected sidewall-oiisaid housingbeingfiormed withianextemal recess, means mounted invsaidt external 1 recess for carrying said handset when not-in use, and said, handset provided with a retractile. cable having conductors which connect the'handset to'the. input'ot said transmitter and, to the output of said receiver, whereby all ele-- ments: of the equipment unit are protected.

against-injury; when the housing is being carried 7 during ,noncommunication periods-and the unit can beusedwhen the housingis-beinsucarriedl 3.. In a portable equipmentmnit for, a two-way inductive carriercommunication-system, the com?- binationcomprising, a suitacasetformiof animus-- ing-tofalightweight material and having ,means to: enableithe housingto bercarried, Van assembly:

includingea transmitter and;-a.r.eceiver of carrier communicationcurrent-mountedlin said housing, a power packincluding abattery mountedinsaid housing, for energizing the transmitter and re-' ceiver, ,a-recess formed in the inside walls; of the housingior the inside longitudinal periphery of the. housing, a .coil of a selected electrical, con-- ductor-mounted-in said recess and provided with 250 connections to the output of said transmitter and to the input of said receiver, said coil beingan air core inductor which isfreefromsaid as"- sembly-and-powerpackandfwhich can be disposed for efiective transmission and reception. of car so rier= communication current by induction: when handset being, provided witha-retractile cordhavingtconductors which'connect said handset 40 asaidzcord to selectively connect-said battery -either 45,. larcase provided? with means to enable the casethe 'housing, is being carried,- 1 a-"handset provided with a push-to-talk switch, an external recess, formed in a-side wall .of sa-idvhousing, andrprovided;

with. means for" carrying said handset, said tothe input'of said transmitter and to the'output'of said receiver, 7 and' switching means includingisaid- -push=to-talk switch and conductors of to said transmitter or to said:receiver.

-41 Inaportable equipmentunit for a two-way inductive carrier "communication system; the combination comprising, alight'weight'flat rectanguto be carried, ahinged-door provided as amajor section of aselect'edsidewalkof the case, an assembly including a transmitter and areceiver of carrier communicationcurrent mounted in said case, apower pack-includingbatteries mounted in said case, said assemblyand power pack being readily accessible due tosaidthinged door, a recessiformedin the insidewalls'ofthe case for the full inside longitudinalperiphery'ofthe case, acoilof an electrical conductor mounted in said recess to form an inductor of relatively largeair core andiwhich'is out o! thewayof said assembly and power pack; saidinductor 'coil being connectedetothe output of said transmitter andto the input of said receiver in-multiple; a handset which. is" provided: with apush-to--tall: switch, saiddoor formed'with an external' recess, means secured in'said external recess for carrying said handset,- said handset' being; provided with a retractile. cord having conductor-swhich' connect the handset to the input of said transmitter and to the output. of said receiver; and switching means: including said pushr-to talk switch and, conductors of said' cord to connect said batteries;

either to the transmitter or to the receiver.

5-. In an emergency equipment for a two -way carrier. communication system, the combination.

comprising, a firsthand-a second case, each said casebeing provided with carrying: means whichv nable: the.= two cases to= be: independently carried to a given location and disposed adjacent each other, an assembly including a transmitter and a receiver of carrier communication current mounted in said first case, a push-to-talk switch mounted on an external wall of said first case, a power pack mounted in said second case, said power pack including a power source and provided with a plurality of terminals to which different direct voltages are supplied from said source, a plug connector receptacle unit mounted on each of said cases, the receptacle unit of said first case having connections to said transmitter and receiver and the receptacle unit of said second case having connections to said voltage terminals, a cable the two ends of which are provided with plug units which mate one with the receptacle unit of said first case and one with the receptacle unit of said second case, a control relay housed in said first case, a first circuit means including said push-to-talk switch and a selected conductor of said cable and receptacle connections to connect a winding of said relay to a selected one of said voltage terminals to energize or deenergize said relay according as said switch is closed or open, and a second circuit means including contacts of said relay and selected conductors of said cable and receptacle connections to connect said transmitter to selected ones of said voltage terminals or to connect said receiver to selected ones of said voltage terminals according as the relay is energized or deenergized.

6. In an emergency equipment for a two-way carrier communication system, the combination comprising, a first and a second case, each said case being provided with carrying means which enable the two cases to be independently carried to a given location and disposed adjacent each other, an assembly including a transmitter and a receiver of carrier communication current mounted in said first case, a push-to-talk switch mounted on an external wall of said first case, a power pack mounted in said second case, said power pack including a transformer, a rectifier means and a multiple terminal voltage divider; said transformer and rectifier means being connected in such a manner as to supply diiierent selected direct voltages at said terminals of said voltage divider when an alternating voltage is applied to a primary winding of said transformer, said second case being provided with alternating voltage terminals which are connected to said primary winding, a receptacle unit of a plug connector mounted on each of said cases; the receptacle unit of said first case having connections to said transmitter, receiver and push-to-talk switch; the receptacle unit of said second case having connections to said voltage divider terminals, a cable the two ends of which are provided with plug units which mate one with the receptacle unit of the first case and one with the receptacle unit of the second case; and switching means including said push-to-talk switch, said cable and receptacle connections to selectively connect either said receiver or said transmitter to said voltage divider terminals.

1. In an emergency equipment for a two-way carrier communication system, the combination comprising, a first and a second portable case,

an assembly including a transmitter and a receiver of carrier communication current mounted in said first case, a first power. pack including batteries mounted in said first case and having connections for energizing said transmitter and receiver, a push-to-talk switch mounted on an external wall of said first case, control means including said push-to-talk switch and a first conto a primary'winding of the transformer of the network, said second case provided with alternate voltage terminals which are connected to said' primary winding, interconnecting circuit means including receptacle units one mounted on each of said cases and a cable the two ends of which are provided with plug units that mate with said receptacle units, said interconnecting circuit means having connections to said transmitter and receiver and to said terminals of said voltage'di--- vider, a second control relay mounted in said first case and having connections to said interconnecting circuit means to energize the relay and automatically disconnect said batteries from said transmitter and receiver in response to a voltage being applied to a given terminal of said second power pack, and other circuit means including said push-to-talk switch and said first relay and having connections to said interconnecting circuit means to selectively connect said transmitter or said receiver to selected terminals of said voltage divider.

8. In an emergency equipment for a two-way carrier communication system, the combination comprising, a first and a second portable case, an assembly including a transmitter and a receiver of carrier communication current mounted in said first case, a handset having a push-to-talk switch mounted on an external wall of said first case; a power pack, an audio amplifier and a loudspeaker mounted in said second case; said power pack including a power source and provided with a plurality of terminals to which difierent direct voltages are supplied from said source, interconnecting circuit means including receptacle units one mounted on each of said cases and a cable the two ends of which are provided with plug units that mate with said receptacle units, circuit means mounted in said second case to connect said audio amplifier and loud-speaker to selected ones of said terminals, other circuit means mounted in said first case to connect said headset to the input of said transmitter and to the output of said receiver, means including connections of said interconnecting circuit means to couple the input of said audio amplifier to the output of said receiver, and switching means including said push-to-talk switch and connections of said interconnecting circuit means to connect either said transmitter or said receiver to selected terminals of said power pack.

9. In an emergency equipment for a two-way carrier communication system, the combination comprising, a first and a second case each of which is provided with carrying means which enable the two cases'to be independently carried to a given location and placed adjacent each other, an assembly and a first power pack mounted in said first case, said assembly including a transmitter and a receiver of carrier communication current, said first power pack including batteries, a handset having a push-to-talk switch mounted on an external wall of said first case and con- I5 nactedtcsa d transmitter and: sai r ceiv r; audio amplifier, a loud-speaker, a call oscillator and a second power; pack mounted in said second case; said second power pack including a transformer-rectifier-filter network connected in such a manner as to supply different direct voltages to a plurality of terminals when an alternating volt? age is supplied to a primary winding ofthe transformer of the network, alternating voltage terminals mounted on said second case and: connected to said primary winding, an interconnect:

ing, circuit means including receptacle units one mounted on each of said cases and a cable the two ends of which are provided with plug units that mate with said receptacle units, control means including said push-to-talk switch andcontrolled by said interconnecting circuit means to either energize said transmitter and receiver from saidbatteries or to energize the, transmitter and, receiver together with said amplifier and loud-speaker from the voltages supplied to said terminals of the second power pack, a call control switch mounted on said second case, and

other control means including said control switch; and controlled by said interconnecting circuit means to at times energize said call oscillator from voltages supplied to terminals of the secondpower pack and to couple said oscillator to said transmitter.

' EDGAR W. BREISCH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

